JP6976143B2 - Water treatment system and water treatment method - Google Patents

Description

Embodiments of the present invention relate to a water treatment system and a water treatment method .

In a water treatment plant, a flocculant injection control device that controls the injection amount of the flocculant into the raw water to be treated is used. However, it has been difficult to control the injection amount of the flocculant in real time and to an appropriate amount according to the water quality of the raw water by the control by the conventional flocculant injection control device. Therefore, the water quality of the treated water (hereinafter referred to as "treated water") may not be stable, and the injection amount of the flocculant may increase more than necessary.

Japanese Patent No. 352265 Japanese Patent No. 592005 Japanese Patent No. 5131005 Japanese Patent No. 5636263

An object to be solved by the present invention is to provide a flocculant injection control device, a flocculant injection control method, and a flocculant injection control system capable of controlling the injection amount of the flocculant to a more appropriate amount.

The water treatment system of the embodiment includes a pH adjuster injection device, a coagulant injection device, a pH meter, and a coagulant injection control device. The pH adjuster injection device determines the injection amount of the pH adjuster to be injected into the raw water so that the alkalinity of the water to be treated becomes a predetermined value. The coagulant injection device injects a coagulant containing aluminum as a main component into the water to be treated. The pH meter measures the pH of the water to be treated, which is a mixture of raw water, a pH adjuster and an agglutinant. The flocculant injection control device controls the injection amount of the flocculant. The coagulant injection control device has a target value calculation unit and an injection amount control unit. Target value calculation unit Ah, the target value of the charge state of the flocs in the water to be treated is calculated based on the pH of the water to be treated measured by the pH meter. The injection amount control unit sets the coagulant injection amount so that the charge state of the flocs in the water to be treated approaches the target value based on the target value of the charge state of the flocs calculated by the target value calculation unit. Control.

The figure which shows the specific example of the structure of the water treatment plant 1 provided with the flocculant injection control system 2 of 1st Embodiment. The figure which shows the specific example of the relationship between the pH of the water to be treated and the aluminum ratio of the 2nd Embodiment in 1st Embodiment. The figure which shows the relationship between the alkalinity of the water to be treated in 1st Embodiment, and the aluminum ratio of 2nd Embodiment. The figure which shows the specific example of the 1st form aluminum ratio, the 2nd form aluminum ratio, and the 3rd form aluminum ratio in 1st Embodiment. The figure which shows the specific example of the 1st form aluminum ratio, the 2nd form aluminum ratio, and the 3rd form aluminum ratio in 1st Embodiment. The figure explaining the situation which the good floc is formed in the 1st Embodiment. The figure explaining the situation which the defective floc is formed in 1st Embodiment. The figure which shows the specific example of the cell which contains the suspension in 1st Embodiment. The figure which shows the specific example of the functional structure of the control part 83 in 1st Embodiment. The figure which shows the specific example of the relationship between the pH of the water to be treated and the charge state target value in 1st Embodiment. The figure which shows the specific example of the relationship between the pH of the water to be treated and the charge state target value in 1st Embodiment. The figure which shows the specific example of the structure of the water treatment plant 1a provided with the agglutination control system 2a of the 2nd Embodiment. The figure which shows the specific example of the structure of the adjustment apparatus 100 in 2nd Embodiment.

Hereinafter, the water treatment system and the water treatment method of the embodiment will be described with reference to the drawings.

(First Embodiment)
FIG. 1 is a diagram showing a specific example of the configuration of a water treatment plant 1 including the flocculant injection control system 2 of the first embodiment. The water treatment plant 1 is not limited to a specific facility as long as it is a facility having a solid-liquid separation function. The solid-liquid separation function is a function of separating a solid substance such as a suspension contained in a liquid from a liquid by aggregating and precipitating it with a flocculant. The water treatment plant 1 may be, for example, a water purification plant or a water treatment facility provided in various factories such as a paper factory and a food factory. When the water treatment plant 1 is a water purification plant, the raw water is, for example, river water, dam lake water, groundwater, rainwater, and sewage. On the other hand, when the water treatment plant 1 is a paper mill or a food factory, the raw water is, for example, industrial wastewater. Hereinafter, the water treatment plant 1 will be described as a water purification plant as an example.

For example, the water treatment plant 1 shown in FIG. 1 includes a flocculant injection control system 2, a pH adjuster injection device 3, and each water storage unit as means for realizing the solid-liquid separation function. For example, each water reservoir is a landing well 10, a mixing pond 20 (rapid mixing pond), a floc forming pond 30-1 to 30-3, a settling pond 40, a filtration pond 50, and a water purification pond 60. Of each water storage section, the landing well 10 is located most upstream with respect to the flow of the water to be treated. Of each water reservoir, the water purification reservoir 60 is located most downstream with respect to the flow of the water to be treated.

The landing well 10 is a facility that stores the raw water sent to the water treatment plant 1, separates unnecessary substances having a relatively large specific density such as plants and earth and sand from the raw water, and sends the water to the water storage section in the subsequent stage. The raw water referred to here is water to be treated by the water treatment plant 1, and is sent to the landing well 10 from inside and outside the water treatment plant 1. In the following, the water being treated in the water treatment plant 1, including this raw water, will be referred to as "treated water", and the water discharged or reusable after the treatment will be referred to as "treated water". That is, the raw water can be said to be the water to be treated in the initial state.

The landing well 10 is provided with a water quality meter 11. The water quality meter 11 measures the water quality of the water to be treated in the landing well 10. For example, water quality is represented by various quantities such as turbidity, chromaticity, water temperature, conductivity, pH (hydrogen ion concentration index), and alkalinity (acid consumption). The water quality meter 11 transmits information indicating the water quality obtained by measuring these quantities to the flocculant injection control system 2. In the landing well 10, relatively large unnecessary substances such as plants and earth and sand are separated from the water to be treated by sedimentation. The supernatant water from which these unnecessary substances have been separated (hereinafter referred to as “supernatant water”) is sent to the mixing pond 20 in the subsequent stage in a state containing the suspension remaining without being separated by precipitation. A flow rate adjusting valve 13 is provided on the upstream side of the landing well 10, and the flow rate of raw water flowing into the landing well 10 is adjusted by the flow rate adjusting valve 13.

A flow meter 12 is provided in the pipe between the landing well 10 and the mixing pond 20. The flow meter 12 measures the flow rate of the supernatant water sent from the landing well 10 to the mixing pond 20. The flow meter 12 transmits information indicating the flow rate of the supernatant water sent from the landing well 10 to the mixing pond 20 to the coagulant injection control system 2.

The pH adjuster is injected into the pipe (water channel) between the landing well 10 and the mixing pond 20 by the pH adjuster injection device 3. There are acidic and alkaline pH adjusters. For example, sulfuric acid and hydrochloric acid are acidic pH regulators, and sodium hydroxide (also known as caustic soda) is an alkaline pH regulator. The pH adjuster injection device 3 determines whether to inject an acidic or alkaline pH adjuster based on the water quality of the water to be treated, and the alkalinity of the water to be treated in the mixing pond 20 becomes a predetermined value. The injection amount of the pH adjuster is determined so as to be used. For example, when injecting an alkaline pH adjuster, the pH adjuster injection device 3 determines the injection amount so that the alkalinity of the water to be treated in the mixing pond 20 is about 20 ± 5 [mg / l]. The pH adjuster may be directly injected into the mixing pond 20. Further, the injection of the pH adjuster may be realized by a manual operation of a pump or the like, or may be realized by the pH adjuster injection device 3 controlling the electric pump.

The supernatant water is sent from the landing well 10 to the mixing pond 20. The coagulant injection control system 2 injects the coagulant into the water of the admixture pond 20 (hereinafter referred to as “miscible water”). For example, the flocculant includes polyaluminum chloride (PAC: Poly Aluminum Chloride) and aluminum sulfate (aluminum sulfate). Hereinafter, the step of injecting these flocculants or pH adjusters into water is referred to as a "chemical injection step".

Normally, the surface of the suspension is negatively charged in water. On the other hand, the flocculant is positively charged in water. Therefore, the flocculant adheres to the suspension. The flocculant adhering to the suspension brings the surface charge of the suspension closer to 0 [mV] by canceling the negative charge of the suspension. As the surface charge of the suspension approaches 0 [mV], the zeta potential approaches 0 [mV]. Therefore, the flocculant has the effect of weakening the repulsion between the suspensions and increasing the number of collisions. Due to the action of this flocculant, the flocs that collide with each other gradually agglomerate, and the formation of larger flocs is promoted.

The mixing pond 20 is provided with a stirring device 21 and a pH meter 22. The stirring device 21 (rapid stirring device) stirs the water in the mixing pond 20. For example, the stirring device 21 is a flash mixer. A motor is connected to the stirring device 21, and the stirring speed may be variable. The pH meter 22 continuously measures the pH of the water in the mixing pond 20. The pH meter 22 may intermittently measure the pH of the water in the mixing pond 20 at a predetermined cycle. For example, the pH meter 22 measures pH every 10 minutes. The pH meter 22 transmits information indicating the pH value of the water in the mixing pond 20 to the flocculant injection control system 2. The pH meter 22 may be provided in the pipe between the mixing pond 20 and the floc forming pond 30-1.

Of the floc forming ponds 30-1 to 30-3, the floc forming pond 30-1 is located most upstream with respect to the flow of the water to be treated. Of the floc forming ponds 30-1 to 30-3, the floc forming pond 30-3 is located most downstream with respect to the flow of the water to be treated.

Water to be treated is sent from the mixing pond 20 to the floc forming pond 30-1. The floc forming pond 30-1 is provided with a stirring device 31-1. The stirring device 31-1 is driven by a motor to stir the water to be treated in the floc forming pond 30-1. For example, the stirrer 31-1 is a floculator. In the water to be treated, which is agitated by the agitator 31-1, fine flocs repeatedly collide with each other to form flocs having a larger particle size.

Water to be treated is sent from the floc forming pond 30-1 to the floc forming pond 30-2. The floc forming pond 30-2 is provided with a stirrer 31-2. For example, the stirring device 31-2 is a floculator similar to the stirring device 31-1 and stirs the water in the floc forming pond 30-2 with a weaker force than the stirring device 31-1. Similar to the floc forming pond 30-1, in the floc forming pond 30-2, a larger floc is formed by the collision between the flocs due to the stirring of the stirring device 31-2.

Water to be treated is sent to the floc forming pond 30-3 from the floc forming pond 30-2. The floc forming pond 30-3 is provided with a stirring device 31-3. For example, the stirring device 31-3 is a floculator similar to the stirring device 31-2, and stirs the water in the floc forming pond 30-3 with a weaker force than the stirring device 31-2. Similar to the floc forming pond 30-2, in the floc forming pond 30-3, the flocs grow into larger flocs due to the collision between the flocs due to the stirring of the stirring device 31-3. As a result, in the water to be treated of the floc forming pond 30-3, flocs having a larger particle size than those of the floc forming ponds 30-1 and 30-2 are formed. Hereinafter, in the description of matters common to the floc forming ponds 30-1 to 30-3, a part of the reference numeral is omitted, and the floc forming ponds 30-1 to 30-3 are referred to as "flock forming pond 30". ..

Water to be treated is sent to the settling basin 40 from the floc forming basin 30-3. The water to be treated is stored in the settling basin 40 for a predetermined time or longer. This predetermined predetermined time is, for example, 3 hours. In the settling basin 40, flocs are separated from the water to be treated by settling for a predetermined time. Hereinafter, the step of separating the flocs from the water to be treated is referred to as a "separation step". At the most downstream portion of the settling basin 40, at least one of ozone treatment and bioactivated carbon treatment may be further applied to the supernatant water obtained by the sedimentation.

The settling basin 40 is provided with a water quality meter 41. The water quality meter 41 measures the water quality of the supernatant water in the settling basin 40. For example, the water quality meter 41 measures turbidity and chromaticity as the water quality of the supernatant water. The water quality meter 41 measures the water quality of the supernatant water collected from the vicinity of the most downstream side of the settling basin 40. The water quality meter 41 transmits information indicating the water quality obtained by measuring these quantities to the flocculant injection control system 2.

The supernatant water of the settling basin 40 is sent to the filtration basin 50. In the filtration basin 50, the supernatant water sent from the settling basin 40 is filtered. The water filtered by the filtration pond 50 (hereinafter referred to as "clean water") is sent to the water purification pond 60.

Further, the filtration pond 50 is provided with a water level rise measuring device 51. The water level rise measuring device 51 measures the water level of the filtration pond 50. For example, the water level rise measuring device 51 measures the rise in water level based on a plurality of water levels measured at different times. The water level rise measuring device 51 transmits information indicating the water level of the filtration pond 50 to the flocculant injection control system 2.

In the purified water pond 60, the purified water is sterilized with chlorine or the like. The sterilized clean water is sent from the water purification pond 60 to a house or the like. Further, a filtration pond cleaning pump 61 is installed between the water purification pond 60 and the filtration pond 50. The filter pond cleaning pump 61 cleans the filter pond 50 using the water of the water purification pond 60. The wastewater generated by cleaning the filtration pond 50 is sent to the mud drainage pond 62.

In addition to the drainage generated by cleaning the filtration pond 50, sludge collected at the bottoms of the floc forming pond 30 and the settling pond 40 is pulled out and sent to the mud drain pond 62 by a pump (not shown) or the like. The sludge sent to the sludge pond 62 is sent to the sludge treatment facility 63. The sludge sent to the sludge treatment facility 63 is dehydrated and carried out of the water purification plant.

2 to 5 are views for explaining the properties of the flocculant to be injected into the miscible water by the flocculant injection control system 2 of the first embodiment. In general, PAC is often used as a flocculant in water purification plants. PAC is a polymer of aluminum chloride and can exist in various forms in water. Specifically, the PAC has a first form of aluminum (hereinafter referred to as "first form aluminum"), a second form of aluminum (hereinafter referred to as "second form aluminum"), and a third form of aluminum in water. It exists in a state of being mixed with aluminum (hereinafter referred to as "third form aluminum"). The mixing ratio of the first form aluminum, the second form aluminum and the third form aluminum varies depending on the pH or alkalinity of the water to be treated to which the PAC is added.

The first form aluminum is a form in which the PAC is changed to a smaller molecular structure as compared with the second form aluminum or the third form aluminum. The first form aluminum is called monomeric aluminum. The first form aluminum has a smaller contribution to the agglutination reaction than the second form aluminum or the third form aluminum.

The second form aluminum is a form in which PAC is transformed into a polyvalent ionic polymer. The second form aluminum is called polymer aluminum. The second form aluminum greatly contributes to the charge neutralizing action.

The third form aluminum is a form in which PAC is changed into colloidal aluminum having a relatively large molecular structure and insoluble aluminum. The third form aluminum greatly contributes to the cross-linking action in the agglutination reaction. Therefore, the third form aluminum greatly contributes to a state in which the flocs become large and settle easily. When the amount of the third form aluminum is insufficient, the flock does not increase because the cross-linking action does not work well even if the charge neutralization proceeds well. In this case, the turbidity of the water to be treated does not decrease so much because the flocs do not easily settle. From this point of view, the ratio of the second form aluminum to the third form aluminum is important in order to form good (large and good sedimentation) flocs.

Hereinafter, the ratio of the amount of the first form aluminum to the total amount of the first form aluminum amount, the second form aluminum amount and the third form aluminum amount is referred to as "the first form aluminum ratio". Similarly, the ratio of the amount of the second form aluminum to the total amount is referred to as the "second form aluminum ratio", and the ratio of the third form aluminum amount to the total amount is referred to as the "third form aluminum ratio". The first form aluminum ratio, the second form aluminum ratio and the third form aluminum ratio can be measured by, for example, the ferron method.

As described above, the second form aluminum is superior to the first form aluminum and the third form aluminum in the charge neutralizing action on the surface of the suspension. Therefore, suspensions and fine flocs are more effectively aggregated as the ratio of the second form aluminum in water is higher. On the other hand, the third form aluminum is superior to the first form aluminum and the second form aluminum in the cross-linking action between flocs. Therefore, the flocs grown to a certain size are more effectively aggregated as the ratio of the third form aluminum in the water is higher.

FIG. 2 is a diagram showing a specific example of the relationship between the pH of the water to be treated and the ratio of the second form aluminum. The horizontal axis shows the pH of the water to be treated. The vertical axis shows the ratio of the second form aluminum in the water to be treated. The relationship between the pH of the water to be treated and the ratio of the second form aluminum can be obtained by measuring the aluminum concentration of each form by the ferron method or a measuring method based on the ferron method. As shown in FIG. 2, the ratio of the second form aluminum increases as the pH of the water to be treated increases from near neutrality (for example, pH = 7.5) toward the acidic direction (that is, as the pH decreases), and becomes a predetermined pH. It saturates below the threshold (pH = 6.0 in the example of FIG. 2). As described above, it can be seen that the increasing potential of the second form aluminum contained in the water to be treated having a pH value less than the pH threshold value is lower than the increasing potential possessed by the water to be treated having a pH value equal to or higher than the pH threshold value.

FIG. 3 is a diagram showing the relationship between the alkalinity of the water to be treated and the ratio of the second form aluminum. The horizontal axis shows the alkalinity of the water to be treated. The vertical axis shows the ratio of the second form aluminum in the water to be treated. Similar to FIG. 2, the relationship between the alkalinity of the water to be treated and the ratio of the second form aluminum can be obtained by measuring the aluminum concentration of each form. As shown in FIG. 3, the ratio of the second form aluminum becomes higher as the alkalinity of the water to be treated becomes higher, and is saturated at a predetermined alkalinity threshold value (about 30 [mg / l] in the example of FIG. 3) or more. As described above, the increasing potential of the second form aluminum of the water to be treated having an alkalinity value equal to or higher than the alkalinity threshold is lower than the increasing potential of the water to be treated having an alkalinity value of less than the alkalinity threshold. You can see that.

4 and 5 are diagrams showing specific examples of the first form aluminum ratio, the second form aluminum ratio, and the third form aluminum ratio. Specifically, FIG. 4 is obtained by acquiring the same relationships as in FIGS. 2 and 3 for each of the first to third forms of aluminum under a plurality of conditions having different pH and alkalinity. In FIG. 4, Man (n is an integer from 1 to 12) represents the first form aluminum ratio, PAn represents the second form aluminum ratio, and CAN represents the third form aluminum ratio. The total value of the first form aluminum ratio MAn, the second form aluminum ratio PAn, and the third form aluminum ratio CAn is 100 [%].

Here, based on the relationship shown in FIG. 2, the second form aluminum ratio PA4 (pH = 7.5, alkalinity = 10 mg / l) in FIG. 4 is the second form aluminum ratio PA1 (pH =) at the same alkalinity. It can be seen that it is smaller than 6.0, alkalinity = 10 mg / l). Similarly, based on the relationship shown in FIG. 3, the second form aluminum ratio PA9 (pH = 6.0, alkalinity = 30 mg / l) in FIG. 4 is the second form aluminum ratio PA1 (pH = 6) at the same pH. It can be seen that it is larger than 0.0, alkalinity = 10 mg / l). From these facts, it can be seen that the second form aluminum ratio PA9 is larger than the second form aluminum ratio PA4.

Further, FIG. 5 is a bar graph showing the aluminum ratio of each form by taking the case where the alkalinity is 20 [mg / l] in FIG. 4 as an example. As can be seen from FIG. 5, even when the alkalinity is the same, the aluminum ratio of each form differs depending on the pH value. That is, it is important to control the pH of the water to be treated in order to promote the charge neutralization action and the cross-linking action satisfactorily.

Therefore, the flocculant injection control system 2 of the embodiment stores information indicating such a relationship (hereinafter referred to as “ratio information”) in advance. For example, the flocculant injection control system 2 may store the table illustrated in FIG. 4 as ratio information. By storing such ratio information in advance, the flocculant injection control system 2 can estimate the aluminum ratio of each form based on the measured values of pH and alkalinity of the water to be treated.

FIG. 6 is a diagram illustrating a situation in which good flocs are formed. The upper figure of FIG. 6A shows a case where the pH of the water to be treated is (almost) neutral and the amount of aluminum in the second form and the amount of aluminum in the third form in the water to be treated are (almost) the same and appropriate. It shows that good flocs are formed in the above, and shows the change in the amount of the second form aluminum and the third form aluminum which changes depending on the pH. Here, a good floc means a floc having excellent sedimentation property, and specifically, a ratio of a solid substance (suspension) to a gel-like substance in the floc (hereinafter referred to as "density") is good. Means flock. For example, this density can be expressed as the area ratio of the gel-like part to the solid part in the image in which the flocs are captured. FIG. 6B shows a specific example of good flocs formed in such a situation.

As described above, when the amount of the second form aluminum contributing to the charge neutralizing action and the amount of the third form aluminum contributing to the cross-linking action are appropriate amounts with respect to the suspension in the water to be treated, the density becomes high. Flocks that are good and have a reasonably large particle size are formed. Further, in the lower figure of FIG. 6 (A), good flocs as shown in FIG. 6 (B) are formed and settled and separated efficiently, so that the turbidity of the water to be treated is only the separated flocs. It shows that it will decrease from the time of raw water. That is, in a situation where good flocs are formed, the rate of decrease in turbidity of the water to be treated is the highest, and the amount of unnecessary substances (suspension, fine flocs that do not settle, etc.) remaining in the water to be treated is also small. ..

As shown in FIG. 6B, when the ratio of the second form aluminum to the third form aluminum in the water to be treated is appropriate, a floc having a good density filled with solid matter is formed. Also, good flocs are hard to break, and in situations where good flocs are formed, the injected flocculant is incorporated into the flocs without waste. Therefore, by controlling the pH of the water to be treated so that good flocs are formed, the amount of flocculant remaining in the water to be treated can be reduced, and the turbidity of the water to be treated can be made more effective. Can be reduced.

FIG. 7 is a diagram illustrating a situation in which defective flocs are formed. The upper figure of FIG. 7A shows a situation in which flocs are formed in a state where the good agglutination state shown in FIG. 6 is broken. For example, the agglutination state 1 is a state in which the pH is inclined to the acidic side, and the second form aluminum that contributes to the charge neutralization action is excessively present. In such a state, the cross-linking action of the flocs does not work sufficiently, so that even if the density is good, the particle size is small and the flocs having poor sedimentation property are formed as shown in FIG. 7 (B). Therefore, in such an aggregated state, unnecessary substances cannot be sufficiently separated from the water to be treated, and the turbidity of the water to be treated cannot be sufficiently reduced.

On the other hand, the agglutination state 2 is a state in which the pH is inclined toward the alkaline side, and the third form aluminum that contributes to the cross-linking action is excessively present. In such a state, the cross-linking action of the flocs is promoted to form flocs having a large particle size, but as shown in FIG. 7 (C), the proportion of gel-like substances in the entire flocs is high and the density is low. Flock is formed. The flocs formed in this way are fragile, and minute pieces of flocs remain in the water to be treated, and as a result, the turbidity of the water to be treated is increased.

Further, since such floc fragments contain a flocculant, the residual amount of the flocculant in the water to be treated is increased, and the aluminum concentration of the water to be treated is increased. The aluminum remaining in the water to be treated causes clogging of the filtration pond 50 (for example, a sand filtration pond) existing in the subsequent stage. Clogged sand filtration ponds promote an increase in filtration resistance, which increases the frequency of cleaning of the filtration ponds, resulting in increased costs. In addition, since flocs containing a high proportion of gel-like substances contain a large amount of water, they affect the properties of sludge deposited in the lower part of the sedimentation basin 40. Therefore, an increase in flocs with a high proportion of gel-like substances increases the time required for sludge disposal, resulting in an increase in cost.

In the two cases of poor aggregation shown in FIG. 7, even when the injection amount of the flocculant into the raw water was determined to maintain charge neutralization, the pH at the time of aggregation deviated significantly from the vicinity of neutrality. This is a phenomenon that can occur if it does. In order to avoid this, unlike these methods, the flocculant injection control system 2 of the present embodiment does not fix the control target value of the charged state near the charge neutralization, but depends on the pH of the water to be treated and the like. And adjust the control target value. As another workaround, the growth of flocs can be increased by maintaining the pH at an appropriate value while measuring the pH at the time of aggregation, increasing the stirring intensity of the stirring device 21, or lengthening the stirring time. There is also a way to promote it.

Hereinafter, the configuration of the flocculant injection control system 2 of the present embodiment will be described in detail. As shown in FIG. 1, the flocculant injection control system 2 includes a flocculant injection device 70, a flocculant injection control device 80, and a limit adjusting unit 90.

The coagulant injection device 70 acquires information indicating the amount of the coagulant to be injected (hereinafter referred to as “injection amount information”) from the coagulant injection control device 80. The coagulant injection device 70 injects the coagulant into the mixing pond 20 based on the acquired injection amount information. The coagulant injection device 70 includes, for example, a pump as a coagulant injection mechanism. The flocculant may be injected not only into the mixing pond 20 but also into the pipe (water channel) between the mixing pond 20 and the landing well 10.

The flocculant injection control device 80 determines the target value of the flocculation state based on the pH of the water to be treated, and determines the injection amount of the flocculant based on the determined target and the current flocculation state of the flocs. .. The aggregated state of the flocs is expressed by, for example, the flow current value, the average value of the surface charge of the flocs, the zeta potential of the flocs, and the like as an index. The flocculant injection control device 80 in the present embodiment acquires the average value of the surface charge of flocs as an index indicating the flocculation state of flocs, but instead of this, the flow current value and the zeta potential (colloidal charge amount) of flocs are used. It may be acquired as an index of the aggregated state. The flow current value, the average value of the surface charge of the flocs, the zeta potential of the flocs, and the like can be measured by using the water to be treated in which the flocculant is injected.

The coagulant injection control device 80 includes a CPU (Central Processing Unit), a memory, an auxiliary storage device, and the like connected by a bus, and executes a program. The flocculant injection control device 80 functions as a device including an analysis unit 81, a calculation unit 82, and a control unit 83 by executing a program. All or part of each function of the flocculant injection control device 80 is realized by using hardware such as ASIC (Application Specific Integrated Circuit), PLD (Programmable Logic Device) and FPGA (Field Programmable Gate Array). May be good. The program may be recorded on a computer-readable recording medium. The computer-readable recording medium is, for example, a flexible disk, a magneto-optical disk, a portable medium such as a ROM or a CD-ROM, or a storage device such as a hard disk built in a computer system. The program may be transmitted over a telecommunication line.

The analysis unit 81 acquires the electrophoretic rate of flocs existing in the water to be treated by analyzing the information acquired from the water to be treated (mixed water) of the mixing pond 20. Specifically, a part of the admixture water collected from the admixture pond 20 for analysis is housed in a predetermined container (hereinafter referred to as “cell”) and attached to the analysis unit 81. The admixture water is not limited to the admixture pond 20, and may be obtained from the floc forming ponds 30-1 to 30-3. Further, the mixed water may be collected by an operator of the water treatment plant 1 or the like, or may be collected by a dedicated water sampling facility that does not require human labor. The mixed water thus collected contains suspensions and fine flocs. In the following, the mixed water collected in the cell will be referred to as a suspension, if necessary.

FIG. 8 is a diagram showing a specific example of a cell containing a suspension. FIG. 8 shows a cell 200 containing a suspension 300 inside. The material of the cell 200 is a transparent material such as glass or acrylic. The depth (thickness) of the cell 200 in the z-axis direction (vertical direction on the paper surface) is, for example, 1 mm to 3 mm. The cell 200 includes a negative electrode 210 at the positive end of the x-axis in the figure and a positive electrode 220 at the negative end. Further, the negative electrode 210 and the positive electrode 220 are connected to the voltage supply unit 230, and a voltage is applied between the negative electrode 210 and the positive electrode 220 by the voltage supply unit 230. That is, when a voltage is applied between the negative electrode 210 and the positive electrode 220, an electric field is formed through the suspension 300 housed in the cell 200. The applied voltage is, for example, 10 to 20 V. The voltage application time is, for example, 3 to 5 minutes. By applying this voltage, the flocs in the positively or negatively charged suspension 300 move toward the positive electrode or the negative electrode. In the following, the movement speed in the positive direction of the x-axis is represented by a positive value, and the movement speed in the negative direction is represented by a negative value. Similarly, the movement speed in the positive direction of the y-axis is represented by a positive value, and the movement speed in the negative direction of the y-axis is represented by a negative value.

Specifically, fine flocs having a negative surface charge are electrophoresed in the positive electrode 220 direction (that is, the negative direction of the x-axis) by applying a voltage. Therefore, the average rate of electrophoresis of flocs in suspension 300, which has a negative surface charge, is negative. On the other hand, fine flocs having a positive surface charge are electrophoresed in the negative electrode 210 direction (that is, in the positive direction of the x-axis) by applying a voltage. Therefore, the average rate of electrophoresis of flocs in suspension 300, which has a positive surface charge, is positive.

The fine flocs whose surface charge is neutralized float in the suspension 300 without being affected by the electric field even when a voltage is applied. Therefore, the moving direction of the fine flocs whose surface charge is neutralized is not constant even when a voltage is applied. Therefore, the variation in the moving speed of each floc becomes large, and the dispersion of the moving speed becomes large. Therefore, the dispersion value of the moving speed of the fine flocs whose surface charges are neutralized becomes a predetermined value or more. That is, by using this predetermined value as a threshold value and comparing it with the dispersion value of the moving speed of the flocs, it is possible to grasp whether or not the surface charge of the flocs is neutralized.

Specifically, as shown in FIG. 1, the analysis unit 81 includes a light source unit 810, an image pickup unit 811 and a speed measurement unit 812. The light source unit 810 irradiates the cell 200 with light. The light source unit 810 irradiates the cell 200 with, for example, laser light or visible light. The light source unit 810 may be configured so that the intensity and wavelength of the emitted light can be changed. The light emitted from the light source unit 810 passes through the transparent cell 200 and is received by the optical system of the image pickup unit 811.

The image pickup unit 811 is configured by using an image pickup device such as a camera. The image pickup unit 811 receives the scattered light reflected by the surface of the floc electrophoresing in the suspension 300. For example, the imaging unit 811 is installed on the side surface of the cell 200 so that the suspension 300 can be imaged through the transparent side surface of the cell 200. The image pickup unit 811 images the flocs electrophoresing in the suspension 300 by applying a voltage at a predetermined cycle. The predetermined cycle is, for example, a 1/3 second cycle. When the predetermined cycle is a 1/3 second cycle, the image pickup unit 811 generates an image of 3 frames per second. The fine flocs whose surface charge is neutralized float not only in the x-axis direction but also in the y-axis direction. The imaging unit 811 transmits information indicating the image captured by the floc to the speed measuring unit 812 at each imaging cycle.

The speed measurement unit 812 performs image analysis processing by software on the image in which the flocs are captured. The velocity measuring unit 812 measures the position of the flocs electrophoresing in the suspension 300 in the captured moving image for each floc. The speed measuring unit 812 measures the position of each floc at different imaging times. The interval between the first imaging time and the second imaging time is, for example, a 1-second interval or a 1/3 second interval. The speed measuring unit 812 measures the electrophoresis speed of the flocs based on the position of the flocs at the first imaging time and the positions of the flocs at the second imaging time. In addition, the speed measuring unit 812 may measure the average speed of the electrophoresis of the flocs based on the positions of the flocs at two or more imaging times. By such a measuring method, the speed measuring unit 812 measures the electrophoresis speed for each floc. The speed measurement unit 812 transmits information indicating the electrophoresis speed for each floc to the calculation unit 82.

The calculation unit 82 acquires information indicating the electrophoresis speed for each floc. The calculation unit 82 calculates the average value of the electrophoresis speed of each floc based on the acquired information. The calculation unit 82 outputs information indicating the average value of the calculated electrophoresis speed to the control unit 83. The average value calculated here may be replaced with another statistical value as long as it indicates the average value of the electrophoresis speed of each floc.

The control unit 83 controls the injection amount of the flocculant into the miscible water. Specifically, the control unit 83 determines the target value of the charge state of the flocs in the water to be treated (hereinafter referred to as “charge state target value”) based on the pH of the water to be treated, and the determined charge state target value. The amount of flocculant injected is determined based on the current charge state of the flocs in the water to be treated. The control unit 83 transmits the injection amount information indicating the determined coagulant injection amount to the limit adjustment unit 90. The control method may be any feedback control method in which the injection amount of the flocculant is used as the operation amount and the charge state of the flocs is used as the control amount. For example, as the control method, general P control, PI control, or PID control may be used as the feedback control method.

The limit adjusting unit 90 determines the amount of the flocculant to be finally injected based on the injection amount information transmitted from the control unit 83. The limit adjusting unit 90 instructs the coagulant injection device 70 to inject the coagulant at the determined injection amount.

Specifically, the limit adjusting unit 90 monitors so that the amount of the flocculant actually injected does not exceed a preset range. For example, when the pH is on the acidic side, the amount of aluminum in the second form that contributes to the charge neutralization action increases, so when trying to control the injection amount of the flocculant based on the charge state, the flocculant is calculated. The injection volume tends to be low. Therefore, by determining the flocculant injection amount so that the limit adjusting unit 90 does not fall below the lower limit of the injection amount, it is possible to avoid the occurrence of troubles due to the injection amount becoming too small. For example, the lower limit of the coagulant injection amount is 10 [mg / L].

On the other hand, when the pH is on the alkaline side, the amount of aluminum in the second form that contributes to the charge neutralization action is small, so when trying to control the coagulant injection rate based on the charge state, the coagulant injection is calculated. The amount tends to be high. Therefore, by determining the flocculant injection amount so that the limit adjusting unit 90 does not exceed the upper limit value of the injection amount, it is possible to avoid the occurrence of troubles due to the injection amount becoming too large. For example, the upper limit of the coagulant injection amount is 50 [mg / L].

When sodium hydroxide is injected as a pH adjuster, the pH may increase due to the addition of the flocculant, but in general, the pH decreases when the flocculant is added. Therefore, the pH of the mixing pond 20 is generally lower than the pH measured at the landing well 10. In consideration of the fluctuation of pH due to the addition of such a flocculant, an upper limit value or a lower limit value may be set for the pH value of the water in the mixing pond 20. In this case, the flocculant is injected at a timing corresponding to the measurement cycle of the pH meter 22 so that the pH changed by the injection of the flocculant is measured by the pH meter 22. In this case, the limit adjusting unit 90 may monitor the pH measurement result and change the injection amount of the flocculant so that the pH remains within the range from the upper limit value to the lower limit value.

FIG. 9 is a diagram showing a specific example of the functional configuration of the control unit 83. The control unit 83 includes a target value calculation unit 831, a target value correction unit 832, an extreme value control unit 833, and an injection amount control unit 834.

The target value calculation unit 831 acquires information indicating the pH of the water to be treated in the mixing pond 20 (hereinafter referred to as “pH information”) from the pH meter 22, and based on the acquired pH information, determines the pH of the water to be treated. Determine the corresponding charge state target value. The target value calculation unit 831 outputs the determined charge state target value to the target value correction unit 832.

The target value correction unit 832 has a function of correcting the charge state target value based on various factors (hereinafter referred to as “performance factors”) that change the treatment performance of the water treatment plant 1. Here, the treatment performance of the water treatment plant 1 means the high ability of the water treatment plant 1 to remove unnecessary substances from the raw water. In general, the treatment performance of a water treatment plant is influenced by many factors such as the structure of the plant and treatment conditions.

For example, when the water temperature of the water to be treated decreases, the aggregation of flocs is hindered and the treatment performance deteriorates. In this case, the target value correction unit 832 acquires information indicating the water quality of the water to be treated (hereinafter referred to as "water quality information") from the water quality meter 11 or the water quality meter 41, and the water temperature is lowered based on the acquired water quality information. Is detected. In this case, the target value correction unit 832 corrects the charge state target value to the plus side in order to increase the total amount of the coagulant to be injected.

Further, for example, when the stirring strength of the mixing pond 20 (rapid mixing pond) or the floc forming pond 30 (slow speed stirring pond) is designed to be weaker than the standard strength, or when such a design change is made. , The aggregation / precipitation action of flocs is suppressed and the processing performance is lowered. Further, when the residence time of the water to be treated in the mixing pond 20 (rapid mixing pond), the floc forming pond 30 (slow speed stirring pond), and the settling pond 40 is designed to be shorter than the standard, or such a design change is made. If this is done, the processing performance will be similarly reduced. In this case, the target value correction unit 832 detects that the target value needs to be corrected based on the design information, the configuration information, and the like of the water treatment plant 1, and is charged in order to increase the total amount of the coagulant to be injected. Correct the target value to the plus side.

Further, for example, when a structure that promotes flocculation and sedimentation is installed in the sedimentation basin 40, the flocculation / sedimentation action of flocs is promoted and the treatment performance is improved, but the operation of the water treatment plant is more than necessary. It can be costly. In this case, the target value correction unit 832 identifies the presence or absence of such a structure based on design information, configuration information, and the like. When such a structure is installed, the target value correction unit 832 corrects the charge state target value to the negative side in order to reduce the total amount of the coagulant to be injected.

Further, for example, when the water quality near the outlets of the settling basin 40 and the filtration basin 50 is worse than the standard, or when the filtration speed in the filtration basin 50 is faster than the standard, the aggregation state may be deteriorated. be. In this case, the target value correction unit 832 detects the deterioration of the agglutination state based on the water quality information. Alternatively, the target value correction unit 832 detects that the filtration speed has become faster than the reference based on the water level information. In this case, the target value correction unit 832 corrects the charge state target value to the plus side in order to increase the total amount of the coagulant to be injected.

The target value correction unit 832 outputs the charge state target value corrected in this way to the extreme value control unit 833.

The correction of the charge state target value described above is an example of the correction performed by the target value correction unit 832. The target value correction unit 832 may determine based on any information whether or not the charge state target value needs to be corrected as long as the information can be acquired with respect to the water treatment plant 1. Further, the target value correction unit 832 may determine on what basis whether or not the charge state target value needs to be corrected. With such a correction, the flocculant injection control device 80 can suppress the deterioration of the treatment performance of the water treatment plant 1 and optimize the cost for water treatment.

The extreme value control unit 833 has a function of searching for an optimum charge state target value based on the concept of extreme value control. In general, extreme value control observes a change in the controlled variable (or an evaluated variable obtained based on the controlled variable) with respect to a minute vibration of the manipulated variable so that the controlled variable (or the evaluated variable) approaches the extreme value. It is a control method that updates the operation amount. For example, the extremum control unit 833 uses the charge state target value as the operation amount and the cost for treating the water to be treated (hereinafter referred to as “treatment cost”) as the evaluation amount, and the charge state target value at which the treatment cost is minimized. To explore. The evaluation amount does not necessarily have to be the treatment cost, and may be any value as long as it can be optimized in the operation or operation of the water treatment plant 1.

For example, the evaluation amount in the present embodiment includes the cost of the flocculant and the pH adjuster used in the water treatment plant 1, the sludge disposal cost, the cleaning cost of the filtration pond 50, and the power of the mechanical structure included in the water treatment plant 1. It is calculated as the total of various costs such as costs (hereinafter referred to as "total cost"). Further, the total cost may include a cost related to the water quality of the water to be treated (hereinafter referred to as “water quality cost”). For example, the water quality cost can be obtained by converting the water quality into a cost based on the concept of wastewater levy or the like.

The extreme value control unit 833 repeatedly determines and updates the charge state target value so that the processing cost approaches the minimum value based on the charge state target value output from the target value correction unit 832. By repeatedly determining and updating the charge state target value in the extreme value control unit 833, the treatment cost required for the operation of the water treatment plant 1 can be optimized. The extreme value control unit 833 outputs the charge state target value thus determined to the injection amount control unit 834.

It should be noted that the extreme value control does not necessarily have to be executed all the time, and may be executed when the deviation between the observed evaluation amount and the target value of the evaluation amount exceeds a predetermined threshold value. Further, in the present embodiment, the flocculant injection control device 80 does not necessarily have to include the extremum control unit 833. In that case, the charge state target value acquired by the target value correction unit 832 may be input to the injection amount control unit 834.

The injection amount control unit 834 acquires information indicating the average value of the electrophoresis speed of the water to be treated from the calculation unit 82. The injection amount control unit 834 estimates the current charge state (surface charge) of the flocs in the water to be treated based on the acquired average value of the electrophoresis speed, and the estimated current charge state and the target value calculation unit 831 The injection amount of the flocculant is determined based on the transmitted charge state target value. The injection amount control unit 834 transmits the determined coagulant injection amount to the limit adjustment unit 90.

Generally, when the injection amount of the flocculant is insufficient, the average value of the surface charge of the suspension remains negative and the suspensions repel each other. Therefore, the formation of flocs does not proceed sufficiently when the injection amount of the flocculant is insufficient. On the other hand, when the injection amount of the flocculant is excessive, the average value of the surface charge of the suspension becomes positive and the suspensions repel each other. Therefore, the formation of flocs does not proceed sufficiently even in a situation where the injection amount of the flocculant is excessive.

On the other hand, when the injection amount of the flocculant is appropriate, the surface charge of the suspension is neutralized, and the suspension attracts each other by the action of the intermolecular force. Therefore, the formation of flocs proceeds when the injection amount of the flocculant is appropriate. Therefore, it is desirable that the injection amount of the flocculant is controlled to an appropriate amount that neutralizes the surface charge of the suspension (the zeta potential becomes about 0 [mV]). However, when it is necessary to reduce the amount of the flocculant used, the injection amount of the flocculant is slightly before the surface charge of the suspension is neutralized (the zeta potential becomes about 0 [mV]). It may be controlled in a slightly smaller amount so as to be. In this case, the zeta potential is preferably in the range of -10 mV to -5 mV.

However, even when the charge state target value is set near the zeta potential of 0 mV where the charge is neutralized, the injection amount of the flocculant may not be appropriate. For example, in FIGS. 6 and 7, when the pH is high, the amount of the second form aluminum is small and the amount of the third form aluminum is high. Therefore, the amount of the flocculant to be injected until the charge is neutralized is mainly determined by the abundance ratio of the second form aluminum, and the third form aluminum is increased. Therefore, the amount of the flocculant injected into the water to be treated becomes relatively large. In such a case, even if the charged state is good, the third form aluminum that promotes the cross-linking action is excessively present, so that flocs having a large grain shape but are fragile are likely to be generated. That is, in such a state, by setting the charge state target value to a slightly negative side and reducing the abundance ratio of the third form aluminum, both the second form aluminum and the third form aluminum are effectively used. It can act and achieve the target treated water quality. For this purpose, as shown in FIGS. 10 and 11 described later, the charge state target value may be adjusted according to the pH, not near zero, which is the charge neutralization.

On the other hand, when the pH is low, the amount of the second form aluminum is large and the amount of the third form aluminum is small. Therefore, the amount of the flocculant to be injected until the charge is neutralized is mainly determined by the abundance ratio of the second form aluminum, so that the third form aluminum is reduced. Therefore, the amount of the flocculant injected into the water to be treated is relatively small. In such a case, even if the charged state is good, since there is little third form aluminum that promotes the cross-linking action, flocs having a small grain shape are likely to be generated. That is, in such a state, by setting the charge state target value slightly to the plus side and increasing the abundance ratio of the third form aluminum, both the second form aluminum and the third form aluminum are effective. It is possible to achieve the target treated water quality.

Therefore, the injection amount control unit 834 increases the injection amount of the flocculant when the current charge state is less than the charge state target value. On the other hand, when the current charged state is equal to or higher than the charged state target value, the amount of the flocculant injected is reduced. Here, how much the coagulant injection amount is increased or decreased is set according to the difference between the current charge state and the charge state target value.

The injection amount control unit 834 may determine the injection amount for each time zone when the flocculant is continuously injected, or for each time when the flocculant is sporadically injected. The injection volume may be determined.

Further, for example, the injection amount control unit 834 reduces the injection amount of the flocculant when the direction of electrophoresis is the negative electrode direction (the surface charge of the flocs is positive). In this case, the injection amount control unit 834 transmits information instructing the limit adjustment unit 90 to reduce the injection amount of the flocculant. On the other hand, the injection amount control unit 834 increases the injection amount of the flocculant when the direction of electrophoresis is the positive electrode direction (the surface charge of the flocs is negative). In this case, the injection amount control unit 834 transmits information instructing the limit adjustment unit 90 to increase the injection amount of the flocculant.

10 and 11 are diagrams showing a specific example of the relationship between the pH of the water to be treated and the target value of the charged state. As described above, the ratio of aluminum in each form in the water to be treated varies depending on the pH of the water to be treated. Therefore, as shown in FIG. 10, the charge state target value also changes in real time according to the pH of the water to be treated. The target value calculation unit 831 stores information indicating the relationship as shown in FIG. 10 in advance, and determines the charge state target value according to the measured pH of the water to be treated.

When the pH of the water to be treated changes frequently, in the method of determining the charge state target value based on the relationship shown in FIG. 10, it is necessary to frequently update the charge state target value, and the control is stable. do not do. In such a case, the charge state target value may be defined as a range corresponding to the fluctuation range of pH, as shown in FIG. According to such a definition, the charge state target value may be updated when the charge state of the flocs in the water to be treated exceeds the range of the current target value in response to a change in pH, thereby stabilizing the control. Can be done.

Further, as shown in FIG. 11, the relationship between the pH of the water to be treated and the charge state target value may be defined as a relationship of a plurality of patterns according to matters to be emphasized in plant operation. For example, as shown in FIG. 11, different relationships may be defined for each of the first pattern that emphasizes the quality of treated water, the second pattern that emphasizes the treatment cost, and the third pattern that emphasizes the balance between the two. .. By defining such a relationship, it is possible to select an appropriate charge state target value according to the operation policy of the plant.

The flocculant injection control system 2 of the embodiment configured as described above controls the injection amount of the flocculant into the water to be treated based on the pH of the water to be treated and the charge state target value of the flocs in the water to be treated. Therefore, the injection amount of the flocculant can be controlled to a more appropriate amount.

(Second embodiment)
FIG. 12 is a diagram showing a specific example of the configuration of the water treatment plant 1a including the agglutination control system 2a of the second embodiment. The water treatment plant 1a is different from the water treatment plant 1 of the embodiment in that it includes a flocculant injection control system 2a instead of the flocculant injection control system 2, and further includes a flow rate adjusting device 4 and a stirring intensity adjusting device 5. In FIG. 12, the same configuration as that of the water treatment plant 1 is designated by the same reference numerals as those in FIG. 1, and the description thereof will be omitted below.

The coagulant injection control system 2a is different from the coagulant injection control system 2 of the first embodiment in that it does not include the limit adjusting unit 90 and further includes the adjusting device 100. The adjusting device 100 is configured to be communicable with the pH adjusting agent injection device 3, the flow rate adjusting device 4, the stirring intensity adjusting device 5, the coagulant injection device 70, and the coagulant injection control device 80. In this case, the flocculant injection control device 80 transmits the injection amount information to the adjusting device 100. The adjusting device 100 controls the pH adjusting agent injection device 3, the flow rate adjusting device 4, the stirring intensity adjusting device 5, and the coagulant injection device 70 based on the injection amount information transmitted from the coagulant injection control device 80.

The flow rate adjusting device 4 adjusts the inflow amount of raw water to the landing well 10 based on the control of the coagulant injection control system 2a. Specifically, the flow rate adjusting device 4 adjusts the inflow amount of raw water by controlling the valve opening degree of the flow rate adjusting valve 13.

The stirring intensity adjusting device 5 adjusts the stirring intensity of the stirring devices 31-1 to 1-31-3 provided in the floc forming ponds 30-1 to 30-3 based on the control of the flocculant injection control system 2a.

The adjusting device 100 acquires injection amount information from the coagulant injection control device 80, and based on the acquired injection amount information, the pH adjusting agent injecting device 3, the flow rate adjusting device 4, the stirring intensity adjusting device 5, and the coagulant injecting device 70. To control.

FIG. 13 is a diagram showing a specific example of the configuration of the adjusting device 100 in the second embodiment. The adjusting device 100 includes a CPU, a memory, an auxiliary storage device, and the like connected by a bus, and executes a program. The adjusting device 100 functions as a device including an injection amount information acquisition unit 101, a stirring intensity control unit 102, a flocculant injection control unit 103, a pH adjuster injection control unit 104, and a flow rate control unit 105 by executing a program. In addition, all or a part of each function of the adjustment device 100 may be realized by using hardware such as ASIC, PLD and FPGA. The program may be recorded on a computer-readable recording medium. The computer-readable recording medium is, for example, a flexible disk, a magneto-optical disk, a portable medium such as a ROM or a CD-ROM, or a storage device such as a hard disk built in a computer system. The program may be transmitted over a telecommunication line.

The injection amount information acquisition unit 101 acquires injection amount information from the coagulant injection control device 80, and uses the acquired injection amount information as the stirring intensity control unit 102, the coagulant injection control unit 103, the pH adjuster injection control unit 104, and the flow rate. Output to the control unit 105.

The stirring intensity control unit 102 determines the stirring intensity of the stirring device 31-1 to 1-31-3 based on the injection amount information. The stirring strength control unit 102 controls the stirring device 31-1 to 31-3 so that the water to be treated is stirred at the determined stirring strength in the floc forming ponds 30-1 to 30-3.

The coagulant injection control unit 103 controls the coagulant injection device 70 in the mixing pond 20 so that the coagulant of the injection amount indicated by the injection amount information is injected into the water to be treated.

The pH adjuster injection control unit 104 determines the injection amount of the pH adjuster into the water to be treated based on the injection amount information. The pH adjuster injection control unit 104 controls the pH adjuster injection device 3 so that the determined injection amount of the pH adjuster is injected into the water to be treated sent to the mixing pond 20.

The flow rate control unit 105 determines the inflow amount of raw water to be flowed into the landing well 10 based on the injection amount information. The flow rate control unit 105 controls the flow rate adjusting device 4 so that the determined inflow amount of raw water flows into the landing well 10.

The coagulant injection control system 2a of the second embodiment configured as described above is based on the determined coagulant injection amount, not only the injection of the coagulant but also the injection of the pH adjuster, the inflow of raw water, and the formation of flocs. The stirring intensity in the pond can be controlled. By performing such control, the water treatment process can be controlled more accurately, and the injection amount of the flocculant can be controlled to a more appropriate amount.

The adjusting device 100 may be configured to accept an operation for inputting information by an operator of the water treatment plant 1. For example, the adjusting device 100 accepts input of information indicating the injection amount of the flocculant or the pH adjusting agent, information indicating the flow rate of the raw water flowing into the landing well 10, information regarding the change in the rotation speed of each stirring device, and the like. In this case, the adjusting device 100 may change the coagulant injection amount based on the input information. Further, in this case, the adjusting device 100 may change the rotation speed of each stirring device based on the input information.

Further, the adjusting device 100 may have the function of the limit adjusting unit 90 in the flocculant injection control system 2 of the first embodiment.

According to at least one embodiment described above, the target value calculation unit 831 for calculating the target value of the flock charge state in the water to be treated and the target value of the flock charge state calculated by the target value calculation unit 831 Based on this, the injection amount of the flocculant is controlled to a more appropriate amount by having an injection amount control unit 834 that controls the injection amount of the flocculant so that the charge state of the flocs in the water to be treated approaches the target value. can do.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope of the invention described in the claims and the equivalent scope thereof, as are included in the scope and gist of the invention.

1,1a ... water treatment plant, 2,2a ... flocculant injection control system, 3 ... pH adjuster injection device, 4 ... flow rate adjuster, 5 ... stirring intensity adjuster, 10 ... water well, 11 ... water quality meter, 12 ... Flow meter, 13 ... Flow control valve, 20 ... Mixing pond, 21 ... Stirrer, 22 ... PH meter, 30, 30-1 to 30-3 ... Flock forming pond, 31-1 to 1-3 ... Stirrer, 40 ... Sedimentation pond, 41 ... Water quality meter, 42 ... Filtration time index measuring device, 50 ... Filtration pond, 51 ... Water level rise measuring device, 55 ... Water purification pond, 60 ... Purifying pond, 61 ... Over pond cleaning pump, 62 ... Exhaust Mud pond, 70 ... coagulant injection device, 80, 80a ... coagulant injection control device, 81 ... analysis unit, 810 ... light source unit, 811 ... image pickup unit, 812 ... speed measurement unit, 82 ... calculation unit, 83 ... control unit , 831 ... Target value calculation unit, 832 ... Target value correction unit, 833 ... Extreme value control unit, 834 ... Injection amount control unit, 90 ... Limit adjustment unit, 100 ... Adjustment device, 101 ... Injection amount information acquisition unit, 102 ... Stirring intensity control unit, 103 ... coagulant injection control unit, 104 ... adjuster injection control unit, 105 ... flow control unit, 200 ... cell, 210 ... negative electrode, 220 ... positive electrode, 230 ... voltage supply unit, 300 ... suspension

Claims (9)

A pH adjuster injection device that determines the injection amount of the pH adjuster to be injected into the raw water so that the alkalinity of the water to be treated becomes a predetermined value.
A coagulant injection device that injects a coagulant containing aluminum as a main component into the water to be treated, and
A pH meter that measures the pH of the water to be treated, which is a mixture of the raw water, the pH adjuster, and the flocculant.
With a flocculant injection control device that controls the injection amount of the flocculant
It is a water treatment system equipped with
The flocculant injection control device is
A target value calculation unit that calculates a target value of the charge state of flocs in the water to be treated based on the pH of the water to be treated measured by the pH meter.
Based on the target value of the charge state of flocs calculated by the target value calculation portion, the charged state of the flocs in the water to be treated is, injection rate control for controlling the injection amount of the flocculant so as to come close to the target value Department and
A water treatment system equipped with. The flocculant injection control device is
For each of the plurality of images obtained by capturing the water to be treated with a voltage at a predetermined cycle, the positions of the plurality of flocs appearing in the images are specified, and the flocs are based on the change in the position of the flocs in the plurality of images. Further equipped with an analysis unit for measuring the electrophoresis speed of the floc, which represents the charge state of the
The injection amount control unit controls the injection amount of the flocculant by feedback control based on the target value of the charge state of the flock and the charge state of the flock represented by the electrophoresis rate measured by the analysis unit. The water treatment system according to claim 1. The flocculant injection control device is
A target value correction unit that corrects the target value according to the occurrence of a factor that affects the aggregation or sedimentation of flocs in the water to be treated.
Further prepare,
The water treatment system according to claim 1 or 2 . The target value correction unit includes the water temperature of the water to be treated, the stirring intensity in the rapid mixing pond that rapidly stirs the water to be treated in which the flocculant is injected, and the residence time of the water to be treated in the rapid mixing pond. The stirring strength in the slow-speed stirring pond that slowly stirs the water to be treated in the subsequent stage of the rapid mixing pond, the residence time of the water to be treated in the slow-speed stirring pond, and the above-mentioned in the subsequent stage of the slow-speed stirring pond. The residence time of the water to be treated in the settling pond that settles and separates the flocs in the water to be treated, the presence or absence of a structure for promoting the settling of flocs in the settling pond, and the water to be treated near the outlet of the settling pond. The occurrence of the factor is based on any one or more of the water quality of the above, the filtration rate in the filter pond that filters the water to be treated in the subsequent stage of the settling pond, and the water quality in the vicinity of the outlet of the filter pond. Detect,
The water treatment system according to claim 3 . The flocculant injection control device is
The injection volume the calculated by the control unit when the injection amount of the aggregating agent is more than a predetermined upper limit value by controlling the injection amount of coagulant below the upper limit, the amount of implanted a predetermined lower limit value of the flocculant If it is smaller than that, a limit adjusting unit for controlling the injection amount of the flocculant to be equal to or higher than the lower limit is further provided.
The water treatment system according to any one of claims 1 to 4 . The spacing regulating unit determines the upper limit value and the lower limit value based on the p H of the water to be treated the pH meter was measured,
The water treatment system according to claim 5 . The flocculant injection control device is
Wherein calculating a processing cost is the cost related to the processing of the water to be treated, and calculated the processing costs, pre SL based on the target value, the target value of charge state such that the processing cost approaches the minimum value Further equipped with an extreme value control unit to be updated,
The water treatment system according to any one of claims 1 to 6. The extreme value control unit uses an amount of a flocculant in the treatment, an amount of a pH adjuster used in the treatment, a cost required for disposing of sludge generated in the treatment, and a filtration pond for filtering the water to be treated. The treatment cost is calculated based on one or more of the cost required for cleaning and the cost required for driving the mechanical structure included in the water treatment system.
The water treatment system according to claim 7 . Determine the injection amount of the pH adjuster to be injected into the raw water so that the alkalinity of the water to be treated becomes a predetermined value.
The pH of the water to be treated, which is a mixture of the raw water, the pH adjuster and an aluminum-based flocculant, is measured.
Based on the measured pH of the water to be treated , the target value of the charge state of the flocs in the water to be treated was calculated.
Based on the target value of the charge state of the calculated the flock, the the charged state of the flocs in the water to be treated, to control the injection amount of the flocculant to approach the target value,
The flocculant is injected into the water to be treated according to the injection amount of the flocculant.
Water treatment method.

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